NCR paper roll consists of CB paper, CFB paper and CF paper. The top paper is coated with chromogenic agent on the back, the CFB paper with chromogenic agent on the front, the back with chromogenic agent and the bottom paper with chromogenic agent on the front. NCR paper can be divided into black printing paper, blue printing paper or other color printing paper according to the type of color rendering. At present, the common color rendering of NCR paper is blue. NCR paper roll duplicates because it does not need carbon pad duplicate paper. It is clean and convenient to use and can be used for printers. NCR paper roll is a product with high technology content. With the increase of the amount of NCR paper, the quality requirement of NCR paper is higher and higher. Here I will share the causes and solutions of blue spot on CF surface of CFB paper.

Color rendering mechanism of NCR paper roll

The color rendering mechanism of NCR paper is that after the normal combination of paper, CFB paper and CF paper (in which CFB paper can be linked one or more). When used, the pressure from outside (such as pen tip, printer, etc.) causes the microcapsule on the back of CB paper to burst, and the mixed dyes contained in the microcapsule will flow out and react with the chromogenic agent on the CF surface.

Causes and solutions of blue spot paper disease

Blue dot quality of NCR paper usually occurs on CF surface of CFB paper.

There are many factors that cause blue dots on CF surface of CFB paper. We can analyze the reasons from the position, shape and manner of blue dots on paper surface.

(1) In the initial coiling process, if the blue dot paper disease is caused by friction between papers due to the difference of coiling speed, its shape is generally long strip. Increasing the difference of coiling tightness can solve or alleviate this paper disease.

(2) When coating, the paint splashes from both sides of the sheet to the CF surface of the sheet. After drying, it is pressed to produce blue spots. It is caused by the unreasonable adjustment of the angle of the wind knife, which usually occurs on both sides of the sheet. The solution is to adjust the angle of the wind knife and install a baffle on both sides of the back roll to prevent the paint from splashing onto the CF surface.

(3) In the coating process, the blue dot produced by embossing during coiling is due to the high moisture content of the coated paper entering the dryer. Although reducing the moisture content can solve this paper disease, it will reduce the smoothness of CB surface, and then affect the quality. The solution is to install a scraper on the dryer.

(4) The microcapsules in the fixed position of the CFB paper were dislocated and broken, and the mixed dyes flowed out, resulting in blue dots on the CF surface through the base paper. This kind of blue dot is generally scattered and small in shape, which is related to the shrinkage of raw paper. In addition, pinholes in base paper can also cause blue spots. This kind of blue dot caused by the quality problem of base paper, it is better to replace the used base paper.

(5) The quality of microcapsules is not satisfactory. Blue spots are produced when mixed dyes penetrate into CF surface during coating. The blue dots are usually all over the page, with bright colors and inconsistent shapes and sizes. This blue dot paper disease is related to the quality of the capsule. The main reason is that the capsule contains free mixed dyes which penetrate into the CF surface to produce blue dots.